Driving wheel bearing apparatus

ABSTRACT

A driving wheel bearing apparatus has an inner ring  5  secured to a wheel hub  1  by a caulked portion  13 . An outer joint member  14  of a constant velocity universal joint  3  has a shoulder portion  19  and a cylindrical shaft portion. Face splines  19   a  and  13   a  are formed at the end faces of the shoulder portion  19  and the caulked portion  13 . Face splines  19   a  and  13   a  are supported with pressure by a fastening bolt  21  that abuts the outer side end face of the wheel hub  1  and is threadedly connected to an internal thread  20   a  of the shaft portion  20 . Compressive remaining stress is placed on the surfaces of the face splines  19   a  and  13   a  as a result of surface modification, by shot peening. The surface hardness is set at 300 Hv or more.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 12/959,633, filed Dec.3, 2010, now U.S. Pat. No. 8,100,775, which is a continuation ofInternational Application No. PCT/JP2009/002485, filed Jun. 3, 2009which claims priority to Japanese Application Nos. 2008-147034, filedJun. 4, 2008; 2008-150492, filed Jun. 9, 2008; 2008-207117, filed Aug.11, 2008; and 2008-208856, filed Aug. 14, 2008. The disclosures of theabove applications are incorporated herein by reference.

FIELD

The present disclosure relates to a driving wheel bearing apparatus thatrotatably supports a driving wheel of a vehicle, such as an automobileand, more particularly, to a driving wheel bearing apparatus with abearing unit and a constant velocity universal joint that are detachablyunitized.

BACKGROUND

A power transmission device that transfers engine power of a vehicle,such as an automobile, to a wheel has to transfer the power from theengine to the wheel. The device must tolerate radial or axialdisplacement and moment displacement from the wheel. The displacementoccurs when the vehicle bounds or turns while running on a rough roadsurface. One end of a drive shaft provided between the engine side andthe driving wheel side is coupled to a differential via a slidableconstant velocity universal joint. The other end of the shaft is coupledto the wheel via a driving wheel bearing apparatus. The driving wheelbearing apparatus includes a fixed type constant velocity universaljoint.

In recent years, the demand for enhanced fuel efficiency has grownsharply from the viewpoint of savings resources, environmentalpollution, etc. Weight reduction of a wheel bearing apparatus, inparticular, of the automobile parts has long received attention andstrongly desired as a factor that fulfills such demands. Variousproposals for a wheel bearing apparatus designed to achieve weightreduction have been made. It also becomes important to reduce costs bysimplifying assembly and disassembly operations in an assembly site ofthe automobile or the like or a maintenance market.

A driving wheel bearing apparatus shown in FIG. 29 is a typical examplethat fulfils such demands. This driving wheel bearing apparatus has astructure where a double row rolling bearing 101 and a constant velocityuniversal joint 102 are detachably unitized. The double row rollingbearing 101 includes an outer member 103 with a body mounting flange 103b to be mounted on a car body. The body mounting flange 103 b isintegrally formed with the outer member 103. The outer member 103 hasdouble row outer raceway surfaces 103 a and 103 a formed on its innercircumference. An inner member 106 includes a wheel hub 104 and an innerring 105. The wheel hub 104 has a wheel mounting flange 104 b formounting a wheel (not shown). The wheel mounting flange 104 b isintegrally formed at one end of the wheel hub 104. The outercircumference of the wheel hub has an inner raceway surface 104 aarranged opposite to one of the double row outer raceway surfaces 103 aand 103 a. A cylindrical portion 104 c axially extends from the innerraceway surface 104 a. The inner ring 105 is press-fit onto thecylindrical portion 104 c of the wheel hub 104. The inner ring outercircumference includes an inner raceway surface 105 a. The inner racewaysurface 105 a is arranged opposite to the other of the double row outerraceway surfaces 103 a and 103 a. Double row balls 108 and 108 arefreely rollably contained between the raceway surfaces via a cage 107placed between them. In addition, the inner ring 105 is axially securedto the wheel hub 104 by a caulked portion 109. The caulked portion 109is formed by plastically deforming the end of the cylindrical portion104 c. Furthermore, a face spline 109 a is formed at the end face of thecaulked portion 109. The face spline 109 a of the caulked portion 109 isformed while caulking is performed.

Seals 110 and 111 are mounted on the opening of an annular space formedbetween the outer member 103 and the inner member 106. The seals 110,111prevent leakage of grease contained in the bearing and entry ofrainwater, dust, etc. into the bearing from the outside.

The constant velocity universal joint 102 includes an outer joint member112, a joint inner ring 113, a cage 114, and torque transmission balls115. The outer joint member 112 has a cup-shaped mouth portion 116, ashoulder portion 117 that forms the bottom of the mouth portion 116, anda hollow shaft portion 118 that axially extends from the shoulderportion 117. The mouth portion 116, the shoulder portion 117, and theshaft portion 118 are formed integrally in the outer joint member 112.The inner circumference of the shaft portion 118 includes an internalthread 118 a. A face spline 117 a is formed at the end face of theshoulder portion 117. The face spline 117 a engages the face spline 109a formed at the end face of the caulked portion 109. Rotational torquefrom a drive shaft (not shown) is transmitted to the wheel mountingflange 104 b via the constant velocity universal joint 102 and the innermember 106.

A fastening bolt 119 is threadedly connected to the internal thread 118a of the shaft portion 118. The face splines 117 a and 109 a of theouter joint member 112 and the inner member 106, arranged opposite toeach other, are supported with pressure by the fastening bolt 119. Thus,the double row rolling bearing 101 and the constant velocity universaljoint 102 are detachably unitized. This makes it possible to realize areduction in weight and size and simplify disassembly and assemblyoperations (refer to, for example, Patent Document JP-A-63-184501).

This driving wheel bearing apparatus enhances workability since the facespline 109 a is formed while the caulked portion 109 is formed at thetime of the oscillating caulking. Thus, this can reduce costs byreducing the number of processes. Since torque is transmitted by theface splines 109 a and 117 a, it is possible to realize a reduction inweight and size and simplify disassembly and assembly operations.However, since the face spline 109 a is formed while the caulked portion109 is formed at the time of the oscillating caulking, the surface ofthe tooth surface keeps the surface hardness obtained after cold plasticdeformation. Thus, the surface hardness only shows a slight increasecompared to the surface hardness obtained after the wheel hub 104 isforged. Since the fatigue strength generally increases proportionatelywith the surface hardness, a significant increase in the fatiguestrength of the face spline 109 a cannot be expected.

High frequency induction quenching may be performed on the face splines109 a and 117 a to increase the surface hardness. These increases wearresistance and fatigue strength. However, this is undesirable becausedoing so not only affects engagement between the face splines 109 a and117 a, due to distortion by heat treatment, but also causes a reductionin toughness due to the high degree of hardness.

SUMMARY

The present disclosure has been made in view of these circumstances.Thus, it is an object of the disclosure to provide a driving wheelbearing apparatus that enhances workability at the time of assembly anddisassembly and increases durability.

It is another object of the disclosure to increase durability byensuring the amount by which an inner ring is squeezed and to reduce thedeformation of the inner ring associated with the oscillating caulking.

Still another object of the disclosure is to enhance the sealingperformance of an engaging portion of the face splines.

To achieve the above objects, a driving wheel bearing apparatus with adouble row rolling bearing and a constant velocity universal joint thatare detachably unitized comprises the double row rolling bearingincluding an outer member with a body mounting flange adapted to bemounted on a car body. The body mounting flange is integrally formed onthe outer circumference of the outer member. A double row outer racewaysurface is integrally formed on the inner circumference of the outermember. An inner member is formed with a wheel hub and an inner ring.The wheel hub has a wheel mounting flange for mounting a wheel. Thewheel mounting flange is integrally formed at one end of the wheel hub.The outer circumference of the wheel hub includes one inner racewaysurface arranged opposite to one of the double row outer racewaysurface. A cylindrical portion axially extends from the inner racewaysurface. The inner ring is press-fit onto the wheel hub. The inner ringouter circumference includes the other inner raceway surface arrangedopposite to the other double row outer raceway surface. A double rowrolling element is freely rollably contained between the racewaysurfaces of the inner member and the outer member. The inner ring issecured to the wheel hub by a caulked portion. The caulked portion isformed by plastically deforming an end of the cylindrical portionradially outward. The constant velocity universal joint has an outerjoint member with a cup-shaped mouth portion, a shoulder portion,forming the bottom of the mouth portion, and a cylindrical shaftportion, axially extending from the shoulder portion. The shaft portionhas an internal thread. The mouth portion, the shoulder portion, and theshaft portion are integrally formed in the outer joint member. Facesplines are formed at the respective end faces of the shoulder portionof the outer joint member and the caulked portion. The face splines aresupported with pressure by a fastening bolt that abuts an outer side endface of the wheel hub. The bolt is threadedly connected to the internalthread of the shaft portion. The double row rolling bearing and theconstant velocity universal joint are coupled together in such a waythat the double row rolling bearing and the constant velocity universaljoint can transmit torque and are axially separable. Compressiveremaining stress is placed on the surfaces of the face splines as aresult of a surface modification.

The driving wheel bearing apparatus has the inner ring secured to thewheel hub by the caulked portion. The caulked portion is formed byplastically deforming an end of the cylindrical portion of the wheel hubradially outward. The face splines are formed at the respective endfaces of the shoulder portion of the outer joint member and the caulkedportion. The face splines are supported with pressure by the fasteningbolt that abuts an outer side end face of the wheel hub. The bolt isthreadedly connected to the internal thread of the shaft portion. Thedouble row rolling bearing and the constant velocity universal joint arecoupled together in such a way that the double row rolling bearing andthe constant velocity universal joint can transmit torque and areaxially separable. Compressive remaining stress is placed on thesurfaces of the face splines as a result of surface modification. Thus,it is possible to increase fatigue strength while keeping an intendedshape and size without deformation caused by heat treatment. Thisprovides a high-quality, high-reliability driving wheel bearingapparatus that increases wear resistance.

The face spline of the caulked portion is formed by plastic deformationwhile the caulked portion is formed. Thus, it is possible to reduce thenumber of processes and reduce costs.

A driving wheel bearing apparatus with a double row rolling bearing anda constant velocity universal joint are detachably unitized comprisingthe double row rolling bearing including an outer member with a bodymounting flange to be mounted on a car body. The body mounting flange isintegrally formed on the outer circumference of the outer member. Theouter member is integrally formed with a double row outer racewaysurface on its inner circumference. An inner member is formed with awheel hub and a cylindrical inner ring member. The wheel hub has a wheelmounting flange for mounting a wheel. The wheel mounting flange isintegrally formed at one end of the wheel hub. The wheel hub outercircumference includes one inner raceway surface arranged opposite toone of the double row outer raceway surface. A cylindrical portionaxially extends from the inner raceway surface. The inner ring member ispress-fit onto the wheel hub. The inner ring outer circumferenceincludes the other inner raceway surface arranged opposite to the otherdouble row outer raceway surface. A double row rolling element is freelyrollably contained between the raceway surfaces of the inner member andthe outer member. The constant velocity universal joint has an outerjoint member with a cup-shaped mouth portion, a shoulder portion thatforms the bottom of the mouth portion, and a cylindrical shaft portionthat axially extends from the shoulder portion. The shaft portion has aninternal thread. The mouth portion, the shoulder portion, and the shaftportion are integrally formed in the outer joint member. Face splinesare formed at the respective end faces of the shoulder portion of theouter joint member and the inner ring member. The face splines aresupported with pressure by a fastening bolt that abuts an outer side endface of the wheel hub. The bolt is threadedly connected to the internalthread of the shaft portion. The double row rolling bearing and theconstant velocity universal joint are coupled together in such a waythat the double row rolling bearing and the constant velocity universaljoint can transmit torque and are axially separable. The wheel hub andthe inner ring member are integrally plastically coupled together.Compressive remaining stress is placed on the surfaces of the facesplines as a result of a surface modification.

The driving wheel bearing apparatus has the face splines formed at therespective end faces of the shoulder portion of the outer joint memberand the inner ring member. The face splines are supported with pressureby the fastening bolt that abuts an outer side end face of the wheelhub. The bolt is threadedly connected to the internal thread of theshaft portion. The double row rolling bearing and the constant velocityuniversal joint are coupled together in such a way that the double rowrolling bearing and the constant velocity universal joint can transmittorque and are axially separable. The wheel hub and the inner ringmember are integrally plastically coupled together. Compressiveremaining stress is placed on the surfaces of the face splines as aresult of surface modification. Thus, it is possible to increase thefatigue strength and wear resistance while keeping an intended shape andsize. This prevents variations or the like due to a gap between theteeth of the face spline or repeated working and thereby increases thereliability.

The face spline of the inner ring member is formed while the inner ringmember is formed by cold forging. Thus, it is possible to enhance theyield of the material.

A step portion is formed at an end of the inner ring member. The facespline is formed at a projecting end face. Thus, it is possible tomeasure the size of a predetermined part by bringing a stylus of ameasuring instrument into contact with the step portion. This makes itpossible to manage the amount of preload of the bearing with ease.

A hardened irregular portion is formed on the inner circumference of thewheel hub. The wheel hub and the inner ring member are integrallyplastically coupled together. A predetermined bearing preload is imposedby fitting a cylindrical part of the inner ring member onto theirregular portion and making the cylindrical part bite into theirregular portion by enlarging the diameter of the cylindrical part.Thus, there is no need to manage the amount of preload by tightlyfastening them with a nut or the like as in the prior art. This makes itpossible to realize a reduction in weight and size, increase thestrength and durability of the wheel hub, and maintain the amount ofpreload for long periods of time.

A cylindrical part of the inner ring member may be fit onto the wheelhub. The wheel hub and the inner ring member may be plasticallyintegrally coupled. A predetermined bearing preload is imposed by acaulked portion formed by plastically deforming an end of thecylindrical part radially outward.

The fastening bolt is threadedly connected to the internal thread of theshaft portion with a spacer placed between the bolt and wheel hub. Thespacer is formed with a substantially L-shaped cross-sectional shape.The spacer has a flange portion that abuts an end face of the wheel hub.A cylindrical part is fit onto the fastening bolt and is guided into thewheel hub. Thus, it is possible to easily perform centering of the outerjoint member and the inner member by the spacer. This simplifiesassembly and disassembly operations of the apparatus. In addition, theface splines can engage with no circumferential and axial looseness.

A guide portion is formed on the inner circumference of a cylindricalpart of the inner ring member. The guide portion projects radiallyinward. The fastening bolt is placed through the guide portion and isthreadedly connected into the internal thread of the shaft portion.Thus, it is possible to perform centering of the outer joint member andthe inner member. This simplifies assembly and disassembly operations ofthe apparatus.

The surface hardness of the face spline is set at 300 Hv or more. Thus,it is possible to maximize the mechanical strength and the fatiguestrength of the material and increase the wear resistance.

The surface of the face spline may be subjected to shot peening or WPCtreatment as a surface modification.

Hardening by laser hardening may be performed on the surface of the facespline. Thus, it is possible to prevent the deformation due to heattreatment and increase the strength and wear resistance of the toothsurface of the face spline. This makes it possible to increase thereliability over a long period of time.

An end of the cylindrical portion, before caulking, is formed as ahollow cylindrical part. An annular groove, with a predetermined depth,is formed on an outer circumferential surface of the cylindrical partfrom a position corresponding to a larger diameter end of the innerraceway surface of the inner ring to a position over a larger end faceof the inner ring. An end of the cylindrical part is plasticallydeformed so that part of the annular groove is brought into intimatecontact with a chamfered portion of the inner ring. The remaining partdoes not make contact with the inner ring and a space is left. Thecylindrical part is easily deformed at the time of caulking. An intendedshape and size of the face spline and the amount by which the inner ringis squeezed are ensured. The deformation of the inner ring associatedwith the oscillating caulking is prevented, making it possible toincrease the durability.

The annular groove is formed in an area ranging from a positioncorresponding to the larger diameter end of the inner raceway surface ofthe inner ring to the chamfered portion on the larger end face side, thearea that slightly spreads over the larger end face. Oscillatingcaulking brings about a state where part of the annular groove isbrought into intimate contact with a chamfered portion of the innerring. The remaining part does not make contact with the inner ring andspace is left. Thus, this makes it possible to ensure a predeterminedamount by which the inner ring is squeezed and prevents the deformationof the inner ring caused by oscillating caulking.

The bottom of the annular groove is formed as a tapered face. It has adiameter that gradually decreases toward the tip of the cylindricalpart. The angle of inclination of the tapered face is set at 15° orless. Thus, it is possible to further reduce the hoop stress produced inthe inner ring at the time of oscillating caulking.

Circular arc surfaces, having radii of curvature Ri and Ro, may beformed on the sides of the annular groove. The radius of curvature Ri ofthe inner side circular arc surface of the circular arc surfaces may besmaller than the radius of curvature Ro of the outer side circular arcsurface (Ri≦Ro). It may be set within a range of R1 to 10.

A chamfered portion, having a circular arc surface with a radius ofcurvature, is formed at an inside diameter end on the larger end faceside of the inner ring. The radius of curvature of the chamfered portionis set within a range of R1.0 to 2.5. Thus, it is possible to preventstress concentration from occurring at the root of the caulked portionwhen a bending moment load is imposed on the apparatus while the vehicleis being operated. This prevents excessive hoop stress from beingproduced in the inner ring by oscillating caulking.

The depth of the annular groove is set at a depth of 0.5 to 2.0 mm.Thus, it is possible to ensure an intended amount by which the innerring is squeezed while preventing deformation of the inner ring.

A hardened layer is formed in the cylindrical portion of the wheel hubby high frequency induction quenching to have a surface hardness of 50to 64 HRC. An inner side edge of the hardened layer is placed within anarea from an outer side starting point in the annular groove to 0 to 4.0mm on the outer side. On the inner side, it is positioned to 0 to 3.0 mmin an area of an outer side circular arc surface of the annular groove.Thus, it is possible to improve the workability of the cylindrical partin the cylindrical portion and prevent cracks or the like fromdeveloping by the plastic deformation.

Two inner rings are press-fit onto the cylindrical portion of the wheelhub. The positions of the inner raceway surfaces of the two inner ringsare the same. The length from the larger diameter end of the innerraceway surface of the inner ring on the caulking side to the larger endface is made longer than the length from the larger diameter end of theinner raceway surface of the other inner ring to the larger end face.Thus, it is possible to prevent the deformation of the inner ring on thecaulking side associated with oscillating caulking.

A seal is mounted on the outside diameter of the inner ring or the innerring member. The seal includes a metal core press-fit onto the outsidediameter of the inner ring or the inner ring member. A seal member, madeof synthetic rubber, is integrally bonded to the metal core byvulcanized adhesion or the like. The seal member has an axial lip. Theaxial lip makes elastic contact with the shoulder portion of the outerjoint member, thus sealing an engaging portion of the face splines.Accordingly, it is possible to prevent foreign matter from the outside,such as rainwater and dust, from entering the engaging portion of theface splines. When dimensional variations occur due to a productionerror or an assembly error in the inner member or the outer jointmember, the seal obtains high sealing performance over a long period oftime because the axial lip has adequate elasticity. This makes itpossible to enhance workability at the time of disassembly and assembly.

The seal member has a side lip slidingly extending radially outward. Astepped portion is formed in the shoulder portion of the outer jointmember. The side lip is brought into elastic contact with the steppedportion. When dimensional variations occur due to a production error oran assembly error in the inner member or the outer joint member, it ispossible to obtain high sealing performance by following the variationsby the deformation of the side lip.

The tip of the axial lip is formed into the shape of a circular arc.When the wheel hub or the outer joint member is deformed due to a heavymoment load imposed on it, it is possible to follow that deformationappropriately, making it possible to obtain high sealing performance.

The seal member has a grease lip. The engaging portion of the facesplines is filled with grease. The grease lip prevents leakage ofgrease. Thus, it is possible to prevent the face splines from wearing.

An exterior seal is mounted on the outside diameter of the shoulderportion of the outer joint member. The exterior seal includes acylindrical metal core and a seal member. The cylindrical metal core ispress-fit onto the outside diameter of the shoulder portion. The sealmember is integrally bonded to the metal core by vulcanized adhesion orthe like. A lip of the seal member is brought into elastic contact withthe inner member or an inner side seal of the seal. This seals theengaging portion of the face splines. Thus, it is possible to preventforeign matter from the outside, such as rainwater and dust, fromentering the engaging portion of the face splines. When dimensionalvariations occur due to a production error or an assembly error in theinner member or the outer joint member, it is possible to obtain highsealing performance over a long period of time due to the seal liphaving adequate elasticity. This makes it possible to enhanceworkability at the time of assembly and disassembly.

The seal member has bifurcating side lips sidlingly extending radially.The side lips are brought into elastic contact with the larger end faceof the inner ring. When dimensional variations occur due to a productionerror or an assembly error in the inner member or the outer jointmember, it is possible to obtain high sealing performance by followingthe variations by the deformation of the side lip.

The seal member has an axial lip with a circular arc tip. The axial lipis brought into elastic contact with the larger end face of the innerring. When the wheel hub or the outer joint member is deformed due to aheavy moment load imposed on it, it is possible to follow thatdeformation appropriately, making it possible to obtain high sealingperformance.

The seal member has a pair of bifurcating radial lips. The radial lipsare brought into elastic contact with the outside diameter of the innerring. When the wheel hub or the outer joint member is deformed due to aheavy moment load imposed on it, it is possible to follow thatdeformation appropriately, making it possible to obtain high sealingperformance.

The inner side seal is formed as a pack seal. The pack seal includesring-shaped seal plate and a slinger with a substantially L-shapedcross-sectional shape. The seal plate is formed with a metal core fitinto the end of the outer member. The metal core has a substantiallyL-shaped cross-sectional shape. A seal member is integrally bonded tothe metal core by vulcanized adhesion. The slinger includes acylindrical part, press-fit onto the outside diameter of the inner ring,and an upstanding portion, extending from the cylindrical part radiallyoutward. The seal member of the exterior seal has a side lip sidlinglyextending radially outward and a radial lip sidlingly extending radiallyinward. The side lip is brought into elastic contact with a side face ofthe upstanding portion of the slinger. The radial lip is brought intoelastic contact with the outside diameter of the inner ring. Thus, it ispossible to prevent foreign matter from the outside, such as rainwaterand dust, from entering the engaging portion of the face splines. Theseal prevents foreign matter, such as rainwater and dust, from enteringthe bearing through a fit portion between the slinger and the innerring. Thus, this increases the durability of the bearing.

A driving wheel bearing apparatus has a double row rolling bearing and aconstant velocity universal joint which are detachably unitized. In theapparatus, the double row rolling bearing includes an outer member. Theouter member has a body mounting flange to be mounted on a car body. Thebody mounting flange is integrally formed on the outer circumference ofthe outer member. The outer member is integrally formed with a doublerow outer raceway surface on its inner circumference. An inner memberincludes a wheel hub and an inner ring. The wheel hub has a wheelmounting flange for mounting a wheel. The wheel mounting flange isintegrally formed at one end of the wheel hub. One inner raceway surfaceis formed on the outer circumference of the wheel hub. The one innerraceway surface is arranged opposite to one of the double row outerraceway surface. A cylindrical portion axially extends from the innerraceway surface. The inner ring is press-fit onto the wheel hub. Theinner ring has the other inner raceway surface formed on its outercircumference. The other inner raceway surface is arranged opposite tothe other double row outer raceway surface. A double row rolling elementis freely rollably contained between the raceway surfaces of the innermember and the outer member. The inner ring is secured to the wheel hubby a caulked portion. The caulked portion is formed by plasticallydeforming an end of the cylindrical portion radially outward. Theconstant velocity universal joint has an outer joint member, having acup-shaped mouth portion, a shoulder portion, forming the bottom of themouth portion, and a cylindrical shaft portion, axially extending fromthe shoulder portion. The shaft portion has an internal thread. Themouth portion, the shoulder portion, and the shaft portion areintegrally formed in the outer joint member. Face splines are formed atthe respective end faces of the shoulder portion of the outer jointmember and the caulked portion. The face splines are supported withpressure by a fastening bolt that abuts an outer side end face of thewheel hub and is threadedly connected to the internal thread of theshaft portion. The double row rolling bearing and the constant velocityuniversal joint are coupled together in such a way that the double rowrolling bearing and the constant velocity universal joint can transmittorque and are axially separable. Compressive remaining stress is placedon the surfaces of the face splines as a result of surface modification.Thus, it is possible to increase fatigue strength while keeping anintended shape and size without deformation caused by heat treatment.This provides a high-quality, high-reliability driving wheel bearingapparatus by increasing wear resistance.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a longitudinal section view of a first embodiment of a drivingwheel bearing apparatus.

FIG. 2 is a longitudinal section view of a bearing unit of FIG. 1.

FIG. 3 is a longitudinal section view of a constant velocity universaljoint of FIG. 1.

FIG. 4 is a longitudinal section view of a second embodiment of thedriving wheel bearing apparatus.

FIG. 5 is a longitudinal section view of a bearing unit of FIG. 4.

FIG. 6 is a longitudinal section view of a third embodiment of thedriving wheel bearing apparatus.

FIG. 7 is a longitudinal section view of a bearing unit of FIG. 6.

FIG. 8 is a longitudinal section view of a fourth embodiment of thedriving wheel bearing apparatus.

FIG. 9 is a longitudinal section view of a fifth embodiment of thedriving wheel bearing apparatus.

FIG. 10 is a longitudinal section view of a bearing unit of FIG. 9.

FIG. 11 is a longitudinal section view of a bearing unit of FIG. 10 withthe bearing unit before oscillating caulking.

FIG. 12 is an enlarged view of the principal portion of FIG. 11.

FIG. 13 is an enlarged view of the principal portion of a modifiedembodiment of FIG. 12.

FIG. 14 is a longitudinal section view of a sixth embodiment of thedriving wheel bearing apparatus.

FIG. 15 is a longitudinal section view of a seventh embodiment of thedriving wheel bearing apparatus.

FIG. 16 is a longitudinal section view of a bearing unit of FIG. 15.

FIG. 17 is an enlarged view of the principal portion of a seal portionof FIG. 15.

FIG. 18 is a modified enlarged view of the principal portion of a sealof FIG. 17.

FIG. 19 is a longitudinal section view of an eighth embodiment of thedriving wheel bearing apparatus.

FIG. 20 is a longitudinal section view of a ninth embodiment of thedriving wheel bearing apparatus.

FIG. 21 is a longitudinal section view of a tenth embodiment of thedriving wheel bearing apparatus.

FIG. 22 is a longitudinal section view of a constant velocity universaljoint of FIG. 21.

FIG. 23 is an enlarged view of the principal portion of an exterior sealportion of FIG. 21.

FIG. 24 is a modified enlarged view of the principal portion of anexterior seal of FIG. 23.

FIG. 25 is another modified enlarged view of the principal portion ofthe exterior seal of FIG. 23.

FIG. 26 is still another modified enlarged view of the principal portionof the exterior seal of FIG. 23.

FIG. 27 is a longitudinal section view of an eleventh embodiment of thedriving wheel bearing apparatus.

FIG. 28 is a longitudinal section view of a twelfth embodiment of thedriving wheel bearing apparatus.

FIG. 29 is a longitudinal section view of an existing driving wheelbearing apparatus.

DETAILED DESCRIPTION

A driving wheel bearing apparatus has a double row rolling bearing and aconstant velocity universal joint that are detachably unitized. Thedouble row rolling bearing includes an outer member that has a bodymounting flange to be mounted on a car body. The body mounting flange isintegrally formed on the outer circumference of the outer member. Theouter member is integrally formed with a double row outer racewaysurface on its inner circumference. An inner member includes a wheel huband an inner ring. The wheel hub has a wheel mounting flange formounting a wheel. The wheel mounting flange is integrally formed at oneend of the wheel hub. One inner raceway surface is formed on the outercircumference of the wheel hub. The one inner raceway surface isarranged opposite to one of the double row outer raceway surface. Acylindrical portion axially extends from the inner raceway surface. Theinner ring is press-fit onto the wheel hub. The inner ring is formedwith the other inner raceway surface on its outer circumference. Theother inner raceway surface is arranged opposite to the other double rowouter raceway surface. A double row rolling element is freely rollablycontained between the raceway surfaces of the inner member and the outermember. The inner ring is secured to the wheel hub by a caulked portion.The caulked portion is formed by plastically deforming the end of thecylindrical portion radially outward. The constant velocity universaljoint has an outer joint member, having a cup-shaped mouth portion, ashoulder portion, forming the bottom of the mouth portion, and acylindrical shaft portion, axially extending from the shoulder portion.The shaft portion has an internal thread. The mouth portion, theshoulder portion, and the shaft portion are integrally formed in theouter joint member. Face splines are formed at the respective end facesof the shoulder portion of the outer joint member and the caulkedportion. The face splines are supported with pressure by a fasteningbolt that abuts an outer side end face of the wheel hub. The bolt isthreadedly connected to the internal thread of the shaft portion. Thedouble row rolling bearing and the constant velocity universal joint arecoupled together in such a way that they can transmit torque and areaxially separable. The face spline of the caulked portion is formed byplastic deformation while the caulked portion is formed. Compressiveremaining stress is placed on the surfaces of the face splines as aresult of a surface modification by shot peening. The surface hardnessis set at 300 Hv or more.

Hereinafter, embodiments of the present disclosure will be described indetail based on the drawings.

FIG. 1 is a longitudinal section view of a first embodiment of a drivingwheel bearing apparatus. FIG. 2 is a longitudinal section view of abearing unit of FIG. 1. FIG. 3 is a longitudinal section view of aconstant velocity universal joint of FIG. 1. Incidentally, in thefollowing description, when the apparatus is mounted on a vehicle, aside that is positioned rather near the outside of a vehicle is referredto as an outer side (a left-hand side of FIG. 1). A side that ispositioned rather near the center of the vehicle is referred to as aninner side (a right-hand side of FIG. 1).

This driving wheel bearing apparatus has a structure that is describedas a so-called third generation. A wheel hub 1, a double row rollingbearing 2, and a constant velocity universal joint 3 are detachablyunitized. The double row rolling bearing 2 includes an outer member 7,an inner member 8, and double row rolling elements (balls) 9 and 9.

The outer member 7 is made of medium/high carbon steel containing 0.40to 0.80 wt % of carbon. The medium/high carbon steel is such as S53C.The outer member 7 has a body mounting flange 7 b to be mounted on a carbody (not shown). The body mounting flange 7 b is integrally formed onthe outer circumference of the outer member 7. The outer member 7 isintegrally formed with double row outer raceway surfaces 7 a and 7 a onits inner circumference. In addition, at least the double row outerraceway surfaces 7 a and 7 a are hardened by high frequency inductionquenching to have a surface hardness of 58 to 64 HRC.

The inner member 8 has double row inner raceway surfaces 1 a and 5 a.The double row inner raceway surfaces 1 a and 5 a are arranged oppositeto the outer raceway surfaces 7 a and 7 a of the outer member 7. Theinner raceway surface 1 a (outer side) is integrally formed with theouter circumference of the wheel hub 1. The inner raceway surface 5 a(inner side) is integrally formed with the outer circumference of theinner ring 5. In this case, the inner member 8 includes the wheel hub 1and the inner ring 5. In addition, the double row rolling elements 9 and9 are contained between the raceway surfaces, and are rollably held bycages 10 and 10. Seals 11 and 12 are mounted on the opening of anannular space formed between the outer member 7 and the inner member 8.The seals 11, 12 prevent leakage of grease contained in the bearing andentry of rainwater, dust, etc. into the bearing from the outside.

As shown in an enlarged view of FIG. 2, the wheel hub 1 has a wheelmounting flange 4 for mounting a wheel (not shown). The wheel mountingflange 4 is integrally formed at an outer side end of the wheel hub. Theinner raceway surface 1 a is formed on the outer circumference of thewheel hub 1. A cylindrical portion 1 b axially extends from the innerraceway surface 1 a. The wheel hub 1 is made of medium/high carbon steelcontaining 0.40 to 0.80 wt % of carbon. The medium/high carbon steel issuch as S53C. An outer circumference surface, that includes the innerraceway surface 1 a, from an inner side base 4 a of the wheel mountingflange 4, the base 4 a serving as a seal land portion of the outer sideseal 11, to the cylindrical portion 1 b is hardened by high frequencyinduction quenching to have a surface hardness of 58 to 64 HRC. This notonly increases the wear resistance of the seal land portion, but alsofurther increases the durability of the wheel hub 1. Thus, the wheel hub1 has adequate mechanical strength for a rotary bending load imposed onthe wheel mounting flange 4. Incidentally, the inner ring 5 and therolling element 9 are made of high-carbon chromium steel such as SUJ2.They are hardened to the core by quenching to have a hardness of 58 to64 HRC.

The inner ring 5 is press-fit onto the cylindrical portion 1 b of thewheel hub 1, via a predetermined interference. The inner ring 5 isaxially secured with an intended bearing preload imposed by a caulkedportion 13. The caulking portion 13 is formed by plastically deformingthe end of the cylindrical portion 1 b. A face spline 13 a is formed byplastic deformation at the end face of the caulked portion 13 whenoscillating caulking is performed. The double row angular ball bearing,using a ball as the rolling element 9, is shown. However, the embodimentis not limited to balls. A double row tapered roller bearing, using atapered roller as the rolling element 9, may be used.

As shown in an enlarged view of FIG. 3, the constant velocity universaljoint 3 is formed with an outer joint member 14, a joint inner ring 15,a cage 16, and a torque transmission ball 17. The outer joint member 14has a cup-shaped mouth portion 18. A shoulder portion 19 forms thebottom of the mouth portion 18. A cylindrical shaft portion 20 axiallyextends from the shoulder portion 19. Curved, axially extending trackgrooves 18 a and 15 a are formed on the inner circumference of the mouthportion 18 and the outer circumference of the joint inner ring 15,respectively. The end face of the shoulder portion 19 includes a facespline 19 a that engages the face spline 13 a of the caulked portion 13.An internal thread 20 a is formed in the shaft portion 20. The outerjoint member 14 is made of medium/high carbon steel containing 0.40 to0.80 wt % of carbon. The medium/high carbon steel is such as S53C. Thetrack groove 18 a is hardened by high frequency induction quenching tohave a surface hardness of 58 to 64 HRC.

As shown in FIG. 1, a fastening bolt 21 is threadedly connected to theinternal thread 20 a of the shaft portion 20. The face splines 19 a and13 a of the shoulder portion 19 of the outer joint member 14 and thecaulked portion 13 of the wheel hub 1 are arranged opposite to eachother and are supported with pressure by the fastening bolt 21. Thedouble row rolling bearing 2 and the constant velocity universal joint 3are thus detachably unitized. In this embodiment, a smaller-diameterportion 1 c is arranged in the inside diameter of the wheel hub 1. Thefastening bolt 21 is inserted, via a predetermined guiding clearance,into the portion 1 c. Thus, it is possible to easily perform centeringof the outer joint member 14 and the inner member 8. This simplifiesassembly and disassembly operations of the apparatus and enables theface splines 19 a and 13 a to engage with no circumferential and axiallooseness or play.

Here, compressive remaining stress is placed on the face spline 13 a ofthe caulked portion 13 and the face spline 19 a of the shoulder portion19 of the outer joint member 14 as a result of surface modification byshot peening. This makes it possible to increase fatigue strength whilekeeping an intended shape and size without deformation caused by heattreatment. As a shot grain, a steel ball having a grain size of severaltens of micrometers to 0.1 mm is used. In addition to a steel ball,nonferrous shot such as ceramic may be used. Incidentally, shot peeningis performed under the following conditions: the pressure is 0.4 MPa,the processing time is 20 seconds, and the injection distance is 100 mm.

In the test conducted by the applicant by using test pieces includingS53C to S55C, it has been found that, although compressive remainingstress slightly differs depending on the shot grain or projectioncondition, it is possible to form compressive remaining stress of 500MPa on the surface by setting the surface hardness of a surface on whichstress is formed at least about 300 HV. Thus, it is possible to formcompressive remaining stress of about 1000 MPa on the uppermost surfacelayer by setting the surface hardness at 520 HV or more. This enablesthe face spline 13 a to also be formed by plastic deformation of thecaulked portion 13. Thus, even when tensile residual stress is producedon the surface, compressive remaining stress is adequately formed onthat surface. As a result, it is possible to maximize the mechanicalstrength and the fatigue strength of the material.

Moreover, in addition to shot peening, as a means for providingcompressive remaining stress, WPC (wide peening cleaning) by which shotgrains are made finer than those in shot peening and are made to hit asurface on which stress is formed at higher speed can be taken up, as anexample. The WPC makes it possible to further increase the fatiguestrength and wear resistance and provide a high-quality,high-reliability driving wheel bearing apparatus.

The surfaces of the face splines 13 a and 19 a may be hardened by laserhardening. By doing so, it is possible to prevent deformation due toheat treatment and increase the strength and wear resistance of thetooth surfaces of the face splines 13 a and 19 a. This makes it possibleto increase the reliability over a long period of time.

Incidentally, as mentioned earlier, both the face splines 13 a and 19 amay be hardened by shot peening, WPC, or laser hardening; however, theembodiment is not limited thereto. Shot peening, WPC, and laserhardening may be appropriately performed in combination. For example,the surface of the face spline 13 a of the caulked portion 13 may behardened by laser hardening, and shot peening may be performed on theface spline 19 a of the shoulder portion 19.

FIG. 4 is a longitudinal section view of a second embodiment of thedriving wheel bearing apparatus. FIG. 5 is a longitudinal section viewof a bearing unit of FIG. 4. This embodiment differs from the firstembodiment, described above, basically only in the structure of thedouble row rolling bearing. Therefore, such components and parts thatfind their identical or functionally equivalent counterparts in thefirst embodiment are identified with the same reference numerals, anddetailed description of them will be omitted.

This driving wheel bearing apparatus has a structure that is describedas a so-called third generation. A wheel hub 22, a double row rollingbearing 23, and a constant velocity universal joint 3 are detachablyunitized. The double row rolling bearing 23 includes an outer member 7,an inner member 24, and double row rolling elements 9 and 9.

As shown in an enlarged view of FIG. 5, the inner member 24 includesdouble row inner raceway surfaces 1 a and 5 a arranged opposite to outerraceway surfaces 7 a and 7 a of the outer member 7. The inner racewaysurface 1 a (outer side) is integrally formed with the outercircumference of the wheel hub 22, and the inner raceway surface 5 a(inner side) is formed integrally with the outer circumference of aninner ring member 25. In this case, the inner member 24 includes thewheel hub 22 and the inner ring member 25.

The wheel hub 22 has a wheel mounting flange 4 integrally formed at anouter side end of the wheel hub 22. The inner raceway surface 1 a isformed on the outer circumference of the wheel hub 22. A cylindricalportion 22 a axially extends from the inner raceway surface 1 a. Theinner circumference of the cylindrical portion 22 includes an irregularportion 26 (crosshatched in the drawing) hardened, by high frequencyinduction quenching, to have a surface hardness of 58 to 64 HRC. Theirregular portion 26 is formed in the shape of a crisscross patternknurls. It includes crossing grooves formed by making a plurality ofannular grooves that are independently formed by turning or the like. Aplurality of axial grooves, that are formed by broaching or the like,intersect at nearly right angles, or crossing grooves are formed byinclined spiral grooves. The tip of the convex portion of the irregularportion 26 is made to have a shape of a spire, such as a triangle, inorder to ensure a good bite.

The wheel hub 22 is made of medium/high carbon steel containing 0.40 to0.80 wt % of carbon. The medium/high carbon steel is such as S53C. Anouter circumference surface, that includes the inner raceway surface 1a, from an inner side base 4 a of the wheel mounting flange 4 to thecylindrical portion 22 a, is hardened by high frequency inductionquenching to have a surface hardness of 58 to 64 HRC (crosshatched inthe drawing). This not only increases the wear resistance of the base 4a, the seal land portion, of the wheel mounting flange 4, but alsofurther increases the durability of the wheel hub 22. Thus, the wheelhub 22 has adequate mechanical strength for a rotary bending loadimposed on the wheel mounting flange 4.

The inner ring member 25 is integrally formed with a cylindrical part 27that axially extends from the inner raceway surface 5 a. The cylindricalpart 27 is formed as a spigot portion 27 a and a fit portion 27. Thespigot portion 27 a is fit into the cylindrical portion 22 a of thewheel hub 22, via a predetermined interference. The fit portion 27 b isformed at the end of the spigot portion 27 a. Also, the fit portion 27 bis arranged opposite to the irregular portion 26 of the wheel hub 22. Astep portion 28 is formed at the inner side end face of the inner ringmember 25. A face spline 25 a is formed at the end face of the stepportion 28. The inner ring member 25 is made of medium/high carbon steelcontaining 0.40 to 0.80 wt % of carbon. The medium/high carbon steel issuch as S53C. A region from the inner raceway surface 5 a to the spigotportion 27 a is hardened by high frequency induction quenching to have asurface hardness of 58 to 64 HRC (crosshatched in the drawing). Thehardness of the fit portion 27 b remains the same as a material hardnessobtained after it is forged.

The wheel hub 22 and the inner ring member 25 are plastically integrallycoupled together with an intended bearing preload imposed by caulking.The fit portion 27 b is made to bite into the irregular portion 26 ofthe wheel hub 22. It is caulked by fitting the cylindrical part 27 ofthe inner ring member 25 into the wheel hub 22 and, at the same time,enlarging the diameter of the fit portion 27 b by squeezing a diameterenlarging jig, such as a mandrel, into the fit portion 27 b. Thiseliminates the need to manage the amount of preload by tightly fasteningthem with a nut or the like as in the prior art. Therefore, it ispossible to realize a reduction in weight and size, increase thestrength and durability of the wheel hub 22, and maintain the amount ofpreload for long periods of time.

The inner ring member 25, including the face spline 25 a, is formed bycold forging. Turning is performed to obtain a predetermined shape andsize. After heat treatment is performed on a predetermined part,compressive remaining stress is placed on the face spline 25 a as aresult of surface modification by shot peening. Thereafter, grinding isperformed on at least the inner raceway surface 5 a. As a result, it ispossible to prevent problems caused by forming the face spline 13 a infinished goods while forming the caulked portion 13 as in the firstembodiment described above. Thus, variations due to a gap between theteeth of the face spline 13 a or repeated working or a reduction indurability due to hoop stress produced in the inner ring 5 areprevented. This makes it possible to provide higher reliability andprevent an increase in costs resulting from the disposal of the finishedgoods due to the above problems.

Here, as shown in FIG. 4, a fastening bolt 21 is threadedly connected tothe internal thread 20 a of the shaft portion 20. The face splines 19 aand 25 a of the outer joint member 14 and the inner member 24, arrangedopposite to each other, are supported with pressure by the fasteningbolt 21. A spacer 29 is placed between the bolt 21 and the wheel hub 22.The double row rolling bearing 23 and the constant velocity universaljoint 3 are detachably unitized. The spacer 29 is formed with asubstantially L-shaped cross-sectional shape. It has a flange portion 29a that abuts the outer side end face of the wheel hub 22. A cylindricalpart 29 b is fit onto the fastening bolt 21. As a result, it is possibleto easily perform centering of the outer joint member 14 and the innermember 24 by the spacer 29. This simplifies assembly and disassemblyoperations of the apparatus. In addition, the face splines 19 a and 25 acan engage with no circumferential and axial looseness or play.

As described above, since the face spline 25 a has no looseness, due tothe spacer 29, and compressive remaining stress is placed thereon as aresult of surface modification by shot peening, the face spline 25 ahardly wears after repeated contact. The face spline 25 a is formed bycold forging to enhance yield; however, the embodiment is not limited.The face spline 25 a may be formed by turning after the inner ringmember 25 is molded by hot forging. The face spline 25 a may be formedby plastic deformation such as orbital forging after being subjected toturning.

FIG. 6 is a longitudinal section view of a third embodiment of thedriving wheel bearing apparatus. FIG. 7 is a longitudinal section viewof a bearing unit of FIG. 6. It is to be noted that components and partsthat find their identical or functionally equivalent counterparts in theabove-described embodiments are identified with the same referencenumerals, and a detailed description will be omitted.

As shown in FIG. 6, the driving wheel bearing apparatus has a structure,which is described as a third generation. A wheel hub 30, a double rowrolling bearing 31, and a constant velocity universal joint 3 aredetachably unitized. As shown in an enlarged view of FIG. 7, the doublerow rolling bearing 31 includes an outer member 7, an inner member 32,and double row rolling elements 9 and 9. The inner member 32 includesthe wheel hub 30 and an inner ring member 33 fit into the wheel hub 30.Double row inner raceway surfaces 1 a and 5 a, formed on the innermember 32, are arranged opposite to outer raceway surfaces 7 a and 7 aof the outer member 7.

The wheel hub 30 has a wheel mounting flange 4 integrally formed at theouter side end of the wheel hub 30. The inner raceway surface 1 a isformed on the outer circumference. A cylindrical portion 22 a axiallyextends from the inner raceway surface 1 a. The wheel hub 30 is made ofmedium/high carbon steel containing 0.40 to 0.80 wt % of carbon. Themedium/high carbon steel is such as S53C. An outer circumferencesurface, that includes the inner raceway surface 1 a, from an inner sidebase 4 a of the wheel mounting flange 4 to the cylindrical portion 22 a,and an inner circumference surface are hardened by high frequencyinduction quenching to have a surface hardness of 58 to 64 HRC (only ahardened portion of the inner circumference surface is crosshatched inthe drawing).

The inner ring member 33 is integrally formed with a cylindrical part 34axially extending from the inner raceway surface 5 a. In addition, theinner ring member 33 and the wheel hub 30 are integrally plasticallycoupled together. A predetermined bearing preload is imposed by acaulked portion 34 a. The caulked portion 34 a is formed by plasticallydeforming the end of the cylindrical part 34 radially outward. The innerring member 33 is made of medium/high carbon steel containing 0.40 to0.80 wt % of carbon. The medium/high carbon steel is such as S53C. Anoutside diameter surface from the inner raceway surface 5 a to thecylindrical part 34 is hardened by high frequency induction quenching tohave a surface hardness of 58 to 64 HRC (crosshatched in the drawing).The hardness of the end of the cylindrical part 34, subjected to plasticdeformation, remains the same as the material hardness obtained after itis forged. The hardness of the caulked portion 34 a is set at 15 to 35HRC, including plastic hardening. This makes it possible to easilyperform plastic deformation and prevent the generation of microcracksassociated with the plastic deformation. At the same time, it ispossible to ensure the strength of the caulked portion 34 a and maintaintight bonding for long periods of time.

In this embodiment, the inner ring member 33, including the face spline25 a, is formed by cold forging. Then, turning is performed to obtain apredetermined shape and size. After heat treatment is performed on apredetermined part, shot peening is performed on the face spline 25 a.Grinding is performed at least on the inner raceway surface 5 a.

As shown in FIG. 6, a fastening bolt 21 is threadedly connected to theinternal thread 20 a of a shaft portion 20. The face splines 19 a and 25a of the outer joint member 14 and the inner member 32, arrangedopposite to each other, are supported with pressure by the fasteningbolt 21. The double row rolling bearing 31 and the constant velocityuniversal joint 3 are detachably unitized.

A spacer 35 is formed with a substantially L-shaped cross-sectionalshape. The spacer 35 has a flange portion 35 a that abuts the end faceof the caulked portion 34 a. A cylindrical part 35 b is fit onto thefastening bolt 21. As a result, it is possible to easily performcentering of the outer joint member 14 and the inner member 32 by thespacer 35. This simplifies assembly and disassembly operations of theapparatus. In addition, it is possible to replace the double row rollingbearing and the constant velocity universal joint separately with a newone without replacing them as a unit as in a fourth-generationstructure. Thus, this contributes to a total cost reduction.

FIG. 8 is a longitudinal section view of a fourth embodiment of thedriving wheel bearing apparatus. This embodiment differs from the thirdembodiment (FIG. 6) described above basically only in part of thestructure of the inner ring member. Therefore, such components and partsthat find their identical or functionally equivalent counterparts in thethird embodiment are identified with the same reference numerals, anddetailed description will be omitted.

This driving wheel bearing apparatus has a structure that which isdescribed as a third generation. A wheel hub 30, a double row rollingbearing 36, and a constant velocity universal joint 3 are detachablyunitized. The double row rolling bearing 36 includes an outer member 7,an inner member 37, and double row rolling elements 9 and 9. The innermember 37 includes the wheel hub 30 and an inner ring member 38 fit intothe wheel hub 30. The inner member 27 has inner raceway surfaces 1 a, 5a formed on its outer circumference. The double row inner racewaysurfaces 1 a and 5 a are arranged opposite to outer raceway surfaces 7 aand 7 a of the outer member 7.

The inner ring member 38 is integrally formed with a cylindrical part 39that axially extends from the inner raceway surface 5 a. In addition,the inner ring member 38 and the wheel hub 30 are integrally plasticallycoupled together. A predetermined bearing preload is imposed by acaulked portion 34 a. The caulked portion 34 a is formed by plasticallydeforming the end of the cylindrical part 39 radially outward. The innerring member 38 is made of medium/high carbon steel containing 0.40 to0.80 wt % of carbon. The medium/high carbon steel is such as S53C. Anoutside diameter surface, from the inner raceway surface 5 a to thecylindrical part 39, is hardened by high frequency induction quenchingto have a surface hardness of 58 to 64 HRC (crosshatched in thedrawing).

The inner circumference of the cylindrical part 39 of the inner ringmember 38 includes a guide portion 39 a. The guide portion 39 a projectsradially inward. A fastening bolt 40 is placed through the guide portion39 a and is threadedly connected to an internal thread 20 a of the shaftportion 20. The face splines 19 a and 25 a of the outer joint member 14and the inner member 37 are supported with pressure by the fasteningbolt 40. The double row rolling bearing 36 and the constant velocityuniversal joint 3 are detachably unitized. As a result, unlike theembodiments described above, it is possible to perform centering of theouter joint member 14 and the inner member 37 without mounting spacers29 and 35 and thereby simplify assembly and disassembly operations ofthe apparatus.

FIG. 9 is a longitudinal section view of a fifth embodiment of thedriving wheel bearing apparatus. FIG. 10 is a longitudinal section viewof a bearing unit of FIG. 9. FIG. 11 is a longitudinal section view of abearing unit of FIG. 10 before oscillating caulking. FIG. 12 is anenlarged view of the principal portion of FIG. 11. FIG. 13 is anenlarged view of the principal portion showing a modified example ofFIG. 12. This embodiment differs from the first embodiment (FIG. 1)described earlier basically only in part of the structure of the innermember. Therefore such components and parts that find their identical orfunctionally equivalent counterparts in the first embodiment areidentified with the same reference numerals, and a detailed descriptionthereof will be omitted.

This driving wheel bearing apparatus has a structure that is describedas a so-called third generation. A wheel hub 41 and a double row rollingbearing 42 are unitized and are detachably axially connected to aconstant velocity universal joint 3. The double row rolling bearing 42includes an outer member 7, an inner member 43, and double row rollingelements 9 and 9.

The outer member 7 is made of medium/high carbon steel containing 0.40to 0.80 wt % of carbon. The medium/high carbon steel is such as S53C. Abody mounting flange 7 b, to be mounted on a car body (not shown), isintegrally formed on the outer circumference of the outer member 7. Theouter member 7 is integrally formed with double row outer racewaysurfaces 7 a and 7 a on its inner circumference. At least the double rowouter raceway surfaces 7 a and 7 a have been formed with a predeterminedhardened layer hardened by high frequency induction quenching to have asurface hardness of 58 to 64 HRC (crosshatched in FIG. 11).

The inner member 43 includes double row inner raceway surfaces 1 a and 5a arranged opposite to the outer raceway surfaces 7 a and 7 a of theouter member 7. The inner raceway surface 1 a (outer side) is directlyformed on the outer circumference of the wheel hub 41. The inner racewaysurface 5 a (inner side) is formed on the outer circumference of theinner ring 5. In this case, the inner member 43 includes the wheel hub41 and the inner ring 5. In addition, the double row rolling elements 9and 9 are contained between the raceway surfaces, and are rollably heldby cages 10 and 10.

As shown in an enlarged view of FIG. 10, the wheel hub 41 has a wheelmounting flange 4 integrally formed on its outer side end. An innerraceway surface 1 a is formed on the outer circumference. A cylindricalportion 1 b axially extends from the inner raceway surface 1 a. Thewheel hub 41 is made of medium/high carbon steel containing 0.40 to 0.80wt % of carbon. The medium/high carbon steel is such as S53C. An outercircumference surface from an inner side base 4 a of the wheel mountingflange 4, the base 4 a serving as a seal land portion of an outer sideseal 11, to the cylindrical portion 1 b, has a hardened layer 46hardened by high frequency induction quenching to have a surfacehardness of 58 to 64 HRC (crosshatched in FIG. 11). The surface hardnessof the inner raceway surface 1 a is set at 58 to 64 HRC. The hardness ofa caulked portion 13, which will be described later, remains the same asa hardness (13 to 30 HRC) obtained after it is forged. This not onlyincreases the wear resistance of the seal land portion, but also furtherincreases the durability of the wheel hub 41. Thus, the wheel hub 41 hasadequate mechanical strength for a rotary bending load imposed on thewheel mounting flange 4.

Face splines 19 a and 13 a of a shoulder portion 19 of an outer jointmember 14 and the caulked portion 13 of the wheel hub 41, arrangedopposite to each other, are supported with pressure as a result of afastening bolt 21 threadedly connected to an internal thread 20 a of ashaft portion 20 as shown in FIG. 9. Thus, the double row rollingbearing 42 and the constant velocity universal joint 3 are detachablyunitized.

As shown in FIG. 11, the cylindrical portion 1 b of the wheel hub 41 isformed as a cylindrical part 44. The cylindrical part 44 has a nearlyuniform thickness before plastic deformation. Circular arc chamferedportions 44 a and 44 b are formed at the end of the cylindrical part 44.In addition, as shown in an enlarged view of FIG. 12, a chamferedportion 5 c, having a circular arc surface with a radius of curvature riof R1.0 to 2.5 mm, is formed at the inside diameter end on the largerend face 5 b side (the caulked portion side) of the inner ring 5. If theradius of curvature ri of the chamfered portion 5 c is set at a valuesmaller than 1.0 mm, there is a possibility that stress concentrationoccurs at the root of the caulked portion 13, when a bending moment loadis imposed on the apparatus while the vehicle is being operated, causesdamage such as microcracks. Conversely, if the radius of curvature riexceeds 2.5 mm, it is undesirable because the inner ring 5 is widenedradially outward when the cylindrical part 44 is plastically deformed,producing excessive hoop stress on the outside diameter of the innerring 5.

An annular groove (undercut) 45 with a depth t is formed on the outercircumference surface of the cylindrical part 44. The annular groove 45is formed in an area ranging from a position corresponding to the largerdiameter end of the inner raceway surface 5 a in the inner ring 5 to thechamfered portion 5 c of the inner ring 5, the area that slightlyspreads over the larger end face 5 b. In addition, a circular arcsurface 45 a, having a radius of curvature Ri, and a circular arcsurface 45 b, having a radius of curvature Ro, are formed at the sidesof the annular groove 45.

In this embodiment, the depth t of the annular groove 45 is set at 0.5to 2.0 mm. The radius of curvature Ri of the inner side circular arcsurface 45 a is set so as to be greater than the radius of curvature riof the chamfered portion 5 c of the inner ring 5 and smaller than theradius of curvature Ro of the outer side circular arc surface 45 b(ri≦Ri≦Ro), and Ri=R1 to 10 mm. As described above, by forming theannular groove 45 on the outer circumference surface of the cylindricalpart 44, the cylindrical part 44 is easily deformed when caulking isperformed. Thus, this makes it possible to prevent the deformation ofthe inner ring 5. However, the effectiveness is reduced if the depth tof the annular groove 45 is smaller than 0.5 mm. If the depth t exceeds2.0 mm, the inner ring is squeezed by an inadequate amount of material.This makes it impossible to obtain the intended power by which the innerring 5 is fixed. That is, after caulking, although part of the annulargroove 45 is brought into intimate contact with the chamfered portion 5c of the inner ring 5, the space of the annular groove 45 remains.

The inner side edge of the hardened layer 46, formed on the outercircumference of the wheel hub 41, is placed within an area from thestarting point of the outer side circular arc surface 45 b in theannular groove 45 up to 4.0 mm on the outer side. On the inner side, itis placed up to 3.0 mm in an area of the circular arc surface 45 b, thearea in the annular groove 45. By placing the position of the inner sideedge of the hardened layer 46 in the above-described area, the amount bywhich the diameter of the inner ring fit portion of the cylindricalportion 1 b is widened by caulking is decreased. This, this makes itpossible to reduce the hoop stress of the inner ring 5. Furthermore, thestarting position of the widened-diameter part can be brought closer tothe caulked portion 13. Thus, this makes it possible to improve thecaulking workability of the cylindrical part 44 in the cylindricalportion 1 b. By placing the inner side edge of the hardened layer 46within an area of the circular arc surface 45 b, it is possible toprevent cracks or the like from developing by the plastic deformation ofthe hardened layer 46.

In this embodiment, the end of the cylindrical portion 1 b in the wheelhub 41, before caulking, is formed as the hollow cylindrical part 44.The annular groove 45, with a predetermined depth t, is formed on theouter circumference surface of the cylindrical part 44. The circular arcsurface 45 a, having a predetermined radius of curvature Ri, and thecircular arc surface 45 b, having a predetermined radius of curvatureRo, are formed on the sides of the annular groove 45. The width of theannular groove 45 is set within a predetermined range. Thus, it ispossible to provide a driving wheel bearing apparatus where thecylindrical part 44 is easily deformed at the time of caulking. Thus,the intended shape and size of the face spline 13 a is obtained. Theinner ring 5 is squeezed by an intended amount. The apparatus increasesits durability by preventing the deformation of the inner ring 5associated with oscillating caulking.

FIG. 13 is a modified example of the cylindrical part 44 shown in FIG.12. This embodiment differs from the embodiment described abovebasically only in the shape of the annular groove. Therefore suchcomponents and parts that find their identical counterparts in theembodiment described above are identified with the same referencenumerals, and overlapping description will be omitted.

The cylindrical portion 1 b of the wheel hub 41 is formed as acylindrical part 44 having a nearly uniform thickness before plasticdeformation. An annular groove 45′ with a depth t is formed on the outercircumference surface of the cylindrical part 44. The annular groove 45′is formed in an area ranging from a position corresponding to the largerdiameter end of the inner raceway surface 5 a in the inner ring 5 to thechamfered portion 5 c of the inner ring 5, the area that slightlyspreads over the larger end face 5 b. In addition, a circular arcsurface 45 a, having a radius of curvature Ri, and a circular arcsurface, having a radius of curvature Ro, are formed at the sides of theannular groove 45′.

The bottom of the annular groove 45′ is formed as a tapered face with adiameter that gradually decreases toward the tip of the cylindrical part44. The angle of inclination θ of the tapered face is set at 15° orless, more preferably, at 10° or less. As a result, it is possible tofurther reduce the hoop stress produced in the inner ring 5 at the timeof oscillating caulking. An angle of inclination θ of more than 15° isundesirable because this makes the cylindrical part 44 thinner andcauses strength reduction.

FIG. 14 is a longitudinal section view of a sixth embodiment of thedriving wheel bearing apparatus. This embodiment differs from the fifthembodiment described above basically only in the structure of the doublerow rolling bearing. Therefore, such components and parts that findtheir identical or functionally equivalent counterparts in the fifthembodiment are identified with the same reference numerals, and adetailed description will be omitted.

This driving wheel bearing apparatus has a structure that is describedas a so-called second generation. A wheel hub 47 and a wheel bearing 48,formed of a double row rolling bearing, are secured to the wheel hub 47.The wheel bearing 48 has a body mounting flange 7 b integrally formed onthe outer circumference of the outer member 7. The outer member 7integrally formed with double row outer raceway surfaces 7 a and 7 a onits inner circumference. Two inner rings 49 and 5 are formed with innerraceway surfaces 5 a and 5 a on their outer circumference. The innerraceway surfaces 5 a and 5 a are arranged opposite to the double rowouter raceway surfaces 7 a and 7 a. Double row rolling elements 9 and 9are rollably contained between the raceway surfaces with cages 10 and 10placed between them. Seals 50 and 12 are mounted on the opening of anannular space formed between the outer member 7 and the two inner rings49 and 5. The seals 50, 12 prevent leakage of grease contained in thebearing and the entry of rainwater, dust, etc. into the bearing from theoutside.

The wheel hub 47 has a wheel mounting flange 4 integrally formed at itsouter side end. A cylindrical portion 47 b axially extends from thewheel mounting flange 4, via the shoulder portion 47 a. In addition, thewheel bearing 48 is press-fit onto the cylindrical portion 47 b of thewheel hub 47, via a predetermined interference, until the wheel bearing48 abuts the shoulder portion 47 a. The wheel bearing 48 is axiallysecured in a state where an intended bearing preload is imposed by acaulked portion 51. The caulked portion 51 is formed by plasticallydeforming the end of the cylindrical portion 47 b. In addition, on theend face of the caulked portion 51, a face spline 51 a is formed bycutting after oscillating caulking.

The wheel hub 47 is made of medium/high carbon steel containing 0.40 to0.80 wt % of carbon. The medium/high carbon steel is such as S53C. Anouter circumference surface from the shoulder portion 47 a of the wheelmounting flange 4 to the cylindrical portion 47 b, includes a hardenedlayer 52 hardened by high frequency induction quenching to have asurface hardness of 50 to 64 HRC (crosshatched in the drawing). Thehardness of the caulked portion 51 remains the same as a hardnessobtained after it is forged. This increases the durability of the wheelhub 47. Thus, the wheel hub 47 has adequate mechanical strength for arotary bending load imposed on the wheel mounting flange 4. This makesit possible to easily perform plastic deformation of the caulked portion51 and cutting of the face spline 51 a.

In this embodiment, as is the case with the embodiment described above,the end of the cylindrical portion 47 b in the pre-caulking wheel hub 47is formed as a hollow cylindrical part. The annular groove 45 is formedon an outer circumference surface of the cylindrical part. The width ofthe annular groove 45 is set within a predetermined range. Thecylindrical part is easily deformed at the time of caulking. The amountby which the inner ring 5 is squeezed is ensured. Thus, deformation ofthe inner ring 5 associated with oscillating caulking can be prevented.

The width dimension of the inner ring 5 on the caulking side (innerside), the inner ring 5 of the two inner rings 49 and 5, is made longerthan the width dimension of the outer side inner ring 49. Specifically,the positions of the inner raceway surfaces 5 a are the same. Thedimension WI from the larger diameter end of the inner raceway surface 5a to the larger end face 5 b is made longer than the dimension Wo fromthe larger diameter end of the inner raceway surface 5 a of the innerring 49 to the larger end face 5 b. This makes it possible to preventthe deformation of the inner ring 5 on the caulking side, thedeformation which would appear at the time of oscillating caulking.

FIG. 15 is a longitudinal section view of a seventh embodiment of thedriving wheel bearing. FIG. 16 is a longitudinal section view of abearing unit of FIG. 15. FIG. 17 is an enlarged view of the principalportion showing a seal portion of FIG. 15. FIG. 18 is an enlarged viewof the principal portion illustrating a modified example of a seal ofFIG. 17. This embodiment differs from the first embodiment (FIG. 1)described earlier basically only in the presence or absence of theexterior seal. Therefore such components and parts that find theiridentical or functionally equivalent counterparts in the firstembodiment are identified with the same reference numerals, and adetailed description will be omitted.

This driving wheel bearing apparatus has a structure that is describedas a so-called third generation. A wheel hub 1, a double row rollingbearing 2, and a constant velocity universal joint 3 are detachablyunitized.

As shown in an enlarged view of FIG. 16, the double row rolling bearing2 includes an outer member 7, an inner member 8, and double row rollingelements 9 and 9. The inner member 8 includes double row inner racewaysurfaces 1 a and 5 a arranged opposite to the outer raceway surfaces 7 aand 7 a of the outer member 7. The inner raceway surface 1 a (outerside) is integrally formed with the outer circumference of the wheel hub1. The inner raceway surface 5 a (inner side) is integrally formed withthe outer circumference of the inner ring 5. In this case, the innermember 8 includes the wheel hub 1 and the inner ring 5.

In this embodiment, as shown in FIG. 15, a stepped portion 53 is formedin a shoulder portion 19 of an outer joint member 14. On the outsidediameter of the inner ring 5, an exterior seal 54 is mounted. Theexterior seal 54 seals an engaging portion of the face splines 19 a and13 a described above. As shown in an enlarged view of FIG. 17, theexterior seal 54 includes a metal core 55 that is formed with acylindrical part 55 a press-fit onto the outside diameter of the innerring 5. An inside diameter portion 55 b extends from the cylindricalpart 55 a radially inward. A seal member 56 is integrally bonded to themetal core 55 by cure adhesion or the like.

The metal core 55 is made of an anticorrosive steel sheet such as anaustenitic stainless steel sheet (such as SUS304 in the JIS), a ferriticstainless steel sheet (such as SUS430 in the JIS), and an anticorrosivecold-rolled steel plate sheet (such as SPCC in the JIS). The metal core55 has a substantially L-shaped cross-sectional shape formed by pressworking. The seal member 56 is made of synthetic rubber such as nitrilerubber. The seal member 56 has a pair of side lips (axial lips) 56 a and56 b that sidlingly extend radially outward, and a grease lip 56 c. Inaddition, the seal lips 56 a, 56 b, and 56 c make elastic contact withthe stepped portion 53 of the shoulder portion 19. This makes itpossible to prevent foreign matter such as rainwater and dust fromentering, from the outside, into the engaging portion of the facesplines 19 a and 13 a. The seal 54 prevents grease, that the engagingportion is filled with, from leaking out. Thus, this prevents the facesplines 19 a and 13 a from corroding or wearing. Furthermore, even whendimensional variations occur due to a production error or an assemblyerror in the inner member 8 or the outer joint member 14, it is possibleto obtain high sealing performance over a long period of time. This isdue to the side lips 56 a and 56 b and the grease lip 56 c havingadequate elasticity.

FIG. 18 is an enlarged view of the principal portion showing a modifiedexample of the exterior seal 54 described above. Components and partsthat find their identical or functionally equivalent counterparts in theembodiment described above are identified with the same referencenumerals, and a detailed description will be omitted.

This exterior seal 57 includes a metal core 55 that includes acylindrical part 55 a, an inside diameter portion 55 b and a seal member58. The cylindrical part 55 a is press-fit onto the outside diameter ofthe inner ring 5. The inside diameter portion 55 b extends radiallyinward from the cylindrical part 55 a. The seal member 58 is integrallybonded to the metal core 55 by cure adhesion or the like. The sealmember 58 is made of synthetic rubber such as nitrile rubber. The sealmember 58 has an axial lip 58 a with a circular arc tip. As a result, itis possible to prevent foreign matter such as rainwater and dust fromthe outside from entering the engaging portion of the face splines 19 aand 13 a. The seal 57 prevents grease, that the engaging portion isfilled with, from leaking out. The exterior seal 57 can be simplifiedand made compact. The abutting portion of the axial lip 58 a is formedto have a circular arc shape. Thus, when the wheel hub 1 or the outerjoint member 14 is deformed, due to a heavy moment load imposed on it,the exterior seal 57 can follow that deformation appropriately, makingit possible to obtain high sealing performance.

FIG. 19 is a longitudinal section view of an eighth embodiment of thedriving wheel bearing apparatus. This embodiment has the same basicstructure as the second embodiment (FIG. 4) described earlier anddiffers from the seventh embodiment (FIG. 15) basically only in thestructure of the double row rolling bearing. Therefore, such componentsand parts that find their identical or functionally equivalentcounterparts in the embodiments described above are identified with thesame reference numerals, and a detailed description will be omitted.

A double row rolling bearing 23 includes an outer member 7, an innermember 24, and double row rolling elements 9 and 9. The inner member 24includes a wheel hub 22 and an inner ring member 25 fit into the wheelhub 22.

The inner ring member 25 is integrally formed with a cylindrical part 27axially extending from an inner raceway surface 5 a. This cylindricalpart 27 is formed of a spigot portion 27 a and a fit portion 27 b. Thespigot portion 27 a is fit into a cylindrical portion 22 a of the wheelhub 22, via a predetermined interference. The fit portion 27 b is formedat the end of the spigot portion 27 a. The fit portion 27 b is arrangedopposite to an irregular portion 26 of the wheel hub 22. A face spline25 a is formed at an inner side end face of the inner ring member 25.The inner ring member 25 is made of medium/high carbon steel containing0.40 to 0.80 wt % of carbon. The medium/high carbon steel is such asS53C. The inner ring member 25 is formed by cold forging or hot forging.

When cold forging is performed, the face spline 25 a is formed whileforging is performed, or the face spline 25 a is formed after coldforging by cold plastic deformation, such as orbital working or bymachining such as cutting. When hot forging is performed, the facespline 25 a is formed after turning by cold plastic deformation, such asorbital working or by machining such as cutting. The inner ring member25 is hardened by high frequency induction quenching, in a region fromthe inner raceway surface 5 a to the spigot portion 27 a, to have asurface hardness of 58 to 64 HRC. The fit portion 27 b remains the sameas a material hardness obtained after it is forged. The face spline 25 amay be formed after high frequency induction quenching.

The wheel hub 22 and the inner ring member 25 are integrally plasticallycoupled together. An intended bearing preload is imposed by caulking bywhich the fit portion 27 b is made to bite into the irregular portion 26of the wheel hub 22. It is caulked by fitting the cylindrical part 27 ofthe inner ring member 25 into the wheel hub 22 and, at the same time,enlarging the diameter of the fit portion 27 b by squeezing a diameterenlarging jig, such as a mandrel, into the fit portion 27 b. Thiseliminates the need to manage the amount of preload by tightly fasteningthem with a nut or the like as in the prior art. Therefore, it ispossible to realize a reduction in weight and size, increase thestrength and durability of the wheel hub 22, and maintain the amount ofpreload for long periods of time.

A fastening bolt 21 is threadedly connected to an internal thread 20 aof the shaft portion 20. Face splines 19 a and 25 a of a shoulderportion 19 of an outer joint member 14 and an inner side end face of theinner ring member 25, arranged opposite to each other, are supportedwith pressure by the fastening bolt 21. A spacer 29 is placed betweenthe bolt 21 and the wheel hub 22. The double row rolling bearing 23 andthe constant velocity universal joint 3 are detachably unitized. Thespacer 29 is formed with a substantially L-shaped cross-sectional shape.A flange portion 29 a abuts the outer side end face of the wheel hub 22.A cylindrical part 29 b is fit onto the fastening bolt 21. As a result,it is possible to easily perform centering of the outer joint member 14and the inner member 24 by the spacer 29. This simplifies assembly anddisassembly operations of the apparatus. In addition, the face splines19 a and 25 a can engage with no circumferential and axial looseness orplay.

In addition, as is the case with the embodiment described above, theoutside diameter of the inner ring 5 includes an exterior seal 54 toseal an engaging portion of the face splines 19 a and 25 a as describedabove. Seal lips 56 a, 56 b, and 56 c make elastic contact with thestepped portion 53 of the shoulder portion 19. This makes it possible toprevent foreign matter, from the outside, such as rainwater and dustfrom entering the engaging portion of the face splines 19 a and 25 a.Also, the seal lips 56 a, 56 b, 56 c prevent grease, that the engagingportion is filled with, from leaking out. Thus, this prevents the facesplines 19 a and 25 a from corroding or wearing. Furthermore, even whendimensional variations occur due to a production error or an assemblyerror in the inner member 24 or the outer joint member 14, it ispossible to obtain high sealing performance over a long period of timesince the side lips 56 a and 56 b and the grease lip 56 c have adequateelasticity.

FIG. 20 is a longitudinal section view of a ninth embodiment of thedriving wheel bearing apparatus. This embodiment has the same basicstructure as the third embodiment (FIG. 6) described earlier and differsfrom the seventh embodiment (FIG. 15) basically only in the structure ofthe double row rolling bearing. Therefore, such components and partsthat find their identical or functionally equivalent counterparts in theembodiments described above are identified with the same referencenumerals, and a detailed description will be omitted.

A double row rolling bearing 31 has an outer member 7, an inner member32, and double row rolling elements 9 and 9. The inner member 32includes a wheel hub 30 and an inner ring member 33 that are press-fitinto the wheel hub 30 and secured via a predetermined interference. Theinner ring member 33 and the wheel hub 30 are integrally plasticallycoupled together with a predetermined bearing preload imposed by acaulked portion 34 a. The caulked portion 34 a is formed by plasticallydeforming the end of the cylindrical part 34 radially outward.

Moreover, as is the case with the embodiments described earlier, theinner ring member 33, including the face spline 25 a, is formed by coldforging or hot forging. However, thermal refining (high-temperaturetempering after quenching) may be performed on the inner ring member 33after it is forged. By performing thermal refining, it is possible toensure low hardness and high toughness.

A fastening bolt 21 is threadedly connected to an internal thread 20 aof the shaft portion 20. Face splines 19 a and 25 a of an outer jointmember 14 and the inner ring member 33, arranged opposite to each other,are supported with pressure by the fastening bolt 21. A spacer 35 isplaced between the bolt and inner member. The double row rolling bearing31 and the constant velocity universal joint 3 are detachably unitized.

In this embodiment, the structure in which the inner ring member 33 ispress-fit into the cylindrical portion 22 a of the wheel hub 30 andsecured to it is taken up as an example. The present disclosure is notlimited to this structure. Though not shown in the drawing, the abovetwo members may be secured to each other by means of a serration formedon the inner circumference of the wheel hub and a serration that engagesthe above serration formed in the cylindrical part of the inner ringmember.

Though not shown in the drawing, the spacer described in the eighth andninth embodiments, having a substantially L-shaped cross-sectional shapeand being used with the fastening bolt, may be used in the seventhembodiment. That is, by doing away with the smaller-diameter portion onthe inside diameter of the wheel hub, through which the fastening boltis placed, makes the inside diameter portion of the wheel hub with acylindrical shape. The flange portion of the spacer abuts on the outerside end face of the wheel hub. The cylindrical inside diameter portionof the wheel hub guides the cylindrical part of the spacer fit onto thefastening bolt. Thus, it is possible to easily perform centering of theouter joint member and the inner member. This simplifies assembly anddisassembly operations of the apparatus. In addition, the face splinescan engage with no circumferential and axial looseness or play. Thus, bydoing away with the smaller-diameter portion, it is possible to achieveweight reduction of the product.

In addition, as is the case with the embodiment described above, anexterior seal 54 is mounted on the outside diameter of the inner ring33. The exterior seal 54 seals an engaging portion of the face splines19 a and 25 a as described above. Seal lips 56 a, 56 b, and 56 c makeelastic contact with a stepped portion 53 of a shoulder portion 19. Thismakes it possible to prevent foreign matter, from the outside, such asrainwater and dust from entering the engaging portion of the facesplines 19 a and 25 a. The seal also prevents grease, that the engagingportion is filled with, from leaking out. Thus, this prevents the facesplines 19 a and 25 a from corroding or wearing. Furthermore, even whendimensional variations occur due to a production error or an assemblyerror in the inner member 32 or the outer joint member 14, it ispossible to obtain high sealing performance over a long period of timedue to the side lips 56 a and 56 b and the grease lip 56 c have adequateelasticity.

FIG. 21 is a longitudinal section view of a tenth embodiment of thedriving wheel bearing apparatus. FIG. 22 is a longitudinal section viewof a constant velocity universal joint of FIG. 21. FIG. 23 is anenlarged view of the principal portion of an exterior seal portion ofFIG. 21. FIG. 24 is an enlarged view of the principal portion showing amodified example of an exterior seal of FIG. 23. FIG. 25 is an enlargedview of the principal portion showing another modified example of theexterior seal of FIG. 23. FIG. 26 is an enlarged view of the principalportion showing still another modified example. This embodiment differsfrom the seventh embodiment (FIG. 15) described earlier basically onlyin the structure of the exterior seal. Therefore such components andparts that find their identical or functionally equivalent counterpartsin the embodiments described above are identified with the samereference numerals, and a detailed description will be omitted.

This driving wheel bearing apparatus has a structure that is describedas a so-called third generation. A wheel hub 1, a double row rollingbearing 2, and a constant velocity universal joint 3 are detachablyunitized. The double row rolling bearing 2 includes an outer member 7,an inner member 8, and double row rolling elements 9 and 9.

An exterior seal 59 for sealing an engaging portion of the face splines19 a and 13 a described above is mounted on a shoulder portion 19 of anouter joint member 14. As shown in FIG. 22, the exterior seal 59includes a cylindrical metal core 60 and a seal member 61. Thecylindrical metal core 60 is press-fit onto the outside diameter of theshoulder portion 19. The seal member 61 is integrally bonded to themetal core 60 by cure adhesion or the like.

The metal core 60 is made of an anticorrosive steel sheet such as anaustenitic stainless steel sheet (such as SUS304 in the JIS), a ferriticstainless steel sheet (such as SUS430 in the JIS), and an anticorrosivecold-rolled steel plate sheet (such as SPCC in the JIS). The metal core60 has a substantially L-shaped cross-sectional shape formed by pressworking. The seal member 61 is made of synthetic rubber such as ACM andNBR. The seal member 61 has a pair of side lips (axial lips) 61 a and 61b sidlingly bifurcating radially. In addition, as shown in an enlargedview of FIG. 23, the seal lips 61 a and 61 b make elastic contact with alarger end face 5 b of an inner ring 5.

This makes it possible to prevent foreign matter, from the outside, suchas rainwater and dust from entering the engaging portion of the facesplines 19 a and 13 a. Also, the seal 61 prevents grease, that theengaging portion is filled with, from leaking out. Thus, this preventsthe face splines 19 a and 13 a from corroding or wearing. Furthermore,even when dimensional variations occur due to a production error or anassembly error in the inner member 8 or the outer joint member 14, it ispossible to obtain high sealing performance over a long period of time.This is due to the side lips 61 a and 61 b having adequate elasticityand making elastic contact with the larger end face 5 b of the innerring 5. The larger end face 5 b has a predetermined surface roughness bygrinding. In addition to the rubber described above, rubbers havingexcellent heat resistance such as HNBR (hydrogenatedacrylonitrile-butadiene rubber), EPDM (ethylene propylene rubber) andFKM (fluorocarbon rubber), EPM (ethylene propylene rubber), siliconrubber can be used as the seal member 61.

FIG. 24 is an enlarged view of the principal portion showing a modifiedexample of the exterior seal 59 described above. It is noted that suchcomponents and parts that find their identical or functionallyequivalent counterparts in the embodiments described above areidentified with the same reference numerals, and a detailed descriptionwill be omitted.

The exterior seal 62 includes a metal core 63 and a seal member 64. Themetal core 63 is formed with a first cylindrical part 63 a press-fitonto the outside diameter of the shoulder portion 19 of the outer jointmember 14. An inclined portion 63 b sidlingly extends from the firstcylindrical part 63 a radially outward. A second cylindrical part 63 caxially extending from the inclined portion 63 b. The seal member 64 isintegrally bonded to the metal core 63 by cure adhesion or the like. Theseal member 64 is made of synthetic rubber such as ACM or NBR. The sealmember 64 has a pair of bifurcating radial lips 64 a and 64 b. The pairof radial lips 64 a and 64 b makes elastic contact with the outsidediameter of the inner ring 5. This makes it possible to prevent foreignmatter, from the outside, such as rainwater and dust, from entering theengaging portion of the face splines 19 a and 13 a. Also, the seal 64prevents grease, that the engaging portion is filled with, from leakingout. Furthermore, since the exterior seal 62 has the pair of radial lips64 a and 64 b, even when the wheel hub 1 or the outer joint member 14 isdeformed due to a heavy moment load imposed on it, the exterior seal 62can follow that deformation appropriately, making it possible to obtainhigh sealing performance.

FIG. 25 is an enlarged view of the principal portion showing anothermodified example of the exterior seal described above. It is noted thatsuch components and parts that find their identical or functionallyequivalent counterparts in the embodiment described above are identifiedwith the same reference numerals, and a detailed description will beomitted.

This exterior seal 65 is formed of a cylindrical metal core 66 and aseal member 67. The cylindrical metal core 66 is press-fit onto theoutside diameter of the shoulder portion 19 of the outer joint member14. The seal member 67 is integrally bonded to the metal core 66 by cureadhesion or the like. The seal member 67 is made of synthetic rubbersuch as ACM or NBR. The seal member 67 has an axial lip 67 a with acircular arc tip. The axial lip 67 a makes elastic contact with thelarger end face 5 b of the inner ring 5. This makes it possible toprevent foreign matter, from the outside, such as rainwater and dust,from entering the engaging portion of the face splines 19 a and 13 a.Also, the seal member 67 prevents grease, that the engaging portion isfilled with, from leaking out. The exterior seal 65 is simplified andthe abutting portion of the axial lip 67 a is formed to have a circulararc shape. When the wheel hub 1 or the outer joint member 14 is deformeddue to a heavy moment load imposed on it, the exterior seal 65 canfollow that deformation appropriately, making it possible to obtain highsealing performance.

FIG. 26 is an enlarged view of the principal portion showing anothermodified example of the exterior seal described above. It is noted thatsuch components and parts that find their identical or functionallyequivalent counterparts in the embodiment described above are identifiedwith the same reference numerals, and a detailed description will beomitted.

This exterior seal 68 includes a cylindrical metal core 69 and a sealmember 70. The cylindrical metal core 69 is press-fit onto the outsidediameter of the shoulder portion 19 of the outer joint member 14. Theseal member 70 is integrally bonded to the metal core 69 by cureadhesion or the like. The seal member 70 is made of synthetic rubbersuch as ACM or NBR. The seal member 70 has a side lip 70 a, sidlinglyextending radially outward, and a radial lip 70 b, sidlingly extendingradially inward. The side lip 70 a makes elastic contact with the sideface of an upstanding portion 74 b of a slinger 74, forming an innerside seal 12. The radial lip 70 b makes elastic contact with the outsidediameter of the inner ring 5.

The inner side seal 12 is formed as a so-called pack seal. It includes aring-shaped seal plate 73 and a slinger 74, with a substantiallyL-shaped cross-sectional shape. The seal plate 73 includes a metal core71 fit into the end of the outer member 7. The metal core 71 has asubstantially L-shaped cross-sectional shape. A seal member 72 isintegrally bonded to the metal core 71 by cure adhesion. The slinger 74includes a cylindrical part 74 a, press-fit onto the outside diameter ofthe inner ring 5, and an upstanding portion 74 b, extending from thecylindrical part 74 a radially outward.

The seal member 72 is made of synthetic rubber such as NBR. The sealmember 72 has a side lip 72 a that makes sliding contact with theupstanding portion 74 b of the slinger 74 with a predetermined axialinterference left between them. A grease lip 72 b and an intermediatelip 72 c are formed into a bifurcated shape. The grease lip 72 b and theintermediate lip 72 c make sliding contact with the cylindrical part 74a, with a predetermined radial interference left between them.

By adopting such a structure, it is possible to prevent foreign matter,from the outside, such as rainwater and dust, from entering the engagingportion of the face splines 19 a and 13 a. The seal prevents grease,that the engaging portion is filled with, from leaking out. Furthermore,since the exterior seal 68 has the side lip 70 a in contact with theslinger 74, it is possible to prevent foreign matter such as rainwaterand dust from entering the bearing through a fit portion between theslinger 74 and the inner ring 5, and thereby increase the durability ofthe bearing.

FIG. 27 is a longitudinal section view of an eleventh embodiment of thedriving wheel bearing apparatus. This embodiment has the same basicstructure as the second embodiment (FIG. 4) described earlier anddiffers from the tenth embodiment (FIG. 21) basically only in thestructure of the double row rolling bearing. Therefore such componentsand parts that find their identical or functionally equivalentcounterparts in the embodiments described above are identified with thesame reference numerals, and a detailed description will be omitted.

A double row rolling bearing 23 includes an outer member 7, an innermember 24, and double row rolling elements 9 and 9. The inner member 24includes a wheel hub 22 and an inner ring member 25 fit into the wheelhub 22.

In this embodiment, an exterior seal 59 is mounted on a shoulder portion19 of an outer joint member 14. Side lips 61 a and 61 b of the exteriorseal 59 make elastic contact with a step portion 28 of the inner ringmember 25. Thus, it seals an engaging portion of face splines 19 a and25 a.

This makes it possible to prevent foreign matter, from the outside, suchas rainwater and dust, from entering the engaging portion of the facesplines 19 a and 25 a. The seal prevents grease, that the engagingportion is filled with, from leaking out. Thus, this prevents the facesplines 19 a and 25 a from corroding or wearing.

FIG. 28 is a longitudinal section view of a twelfth embodiment of thedriving wheel bearing apparatus. This embodiment has the same basicstructure as the third embodiment (FIG. 6) described earlier and differsfrom the tenth embodiment (FIG. 21) basically only in the structure ofthe double row rolling bearing. Therefore, such components and partsthat find their identical or functionally equivalent counterparts in theembodiments described earlier are identified with the same referencenumerals, and a detailed description will be omitted.

A double row rolling bearing 31 includes an outer member 7, an innermember 32, and double row rolling elements 9 and 9. The inner member 32includes a wheel hub 30 and an inner ring member 33 fit into the wheelhub 30 and secured via a predetermined interference.

The inner ring member 33, including a face spline 25 a, is formed bycold forging or hot forging. However, thermal refining (high-temperaturetempering after quenching) may be performed on the inner ring member 33after it is forged. By performing thermal refining, it is possible toensure low hardness and high toughness.

In this embodiment, an exterior seal 59 is mounted on a shoulder portion19 of an outer joint member 14. Side lips 61 a and 61 b of the exteriorseal 59 make elastic contact with a step portion 28 of the inner ringmember 33. Thus, it seals an engaging portion of the face splines 19 aand 25 a.

This makes it possible to prevent foreign matter, from the outside, suchas rainwater and dust, from entering the engaging portion of the facesplines 19 a and 25 a. Also, the seal prevents grease, that the engagingportion is filled with, from leaking out. Thus, it prevents the facesplines 19 a and 25 a from corroding or wearing.

A driving wheel bearing apparatus can be applied to a driving wheelbearing apparatus where a double row rolling bearing has a wheel hub anda constant velocity universal joint that are detachably unitized.

Although the embodiments of the present disclosure have been described,it is to be understood that the embodiments of the present disclosureare by way of illustration and example only and are not to be taken byway of limitation, and the present disclosure may be practiced in anyother manner than specifically described above, with any modificationsor variations made within the spirit of the present disclosure. Thescope of the present disclosure is recited in the appended claims, andincludes any modifications and variations made in the sense and withinthe scope equivalent to what is recited in the claims.

1. A driving wheel bearing apparatus having a double row rolling bearingand a constant velocity universal joint that are detachably unitized,the apparatus comprising: the double row rolling bearing including anouter member with a body mounting flange to be mounted on a car body,the body mounting flange is integrally formed on the outer circumferenceof the outer member, the outer member is integrally formed with doublerow outer raceway surfaces on its inner circumference; an inner memberincluding a wheel hub and an inner ring, the wheel hub includes a wheelmounting flange for mounting a wheel, the wheel mounting flange isintegrally formed at one end of the wheel hub, one inner raceway surfaceformed on the outer circumference of the wheel hub, the one innerraceway surface is arranged opposite to one of the double row outerraceway surfaces, a cylindrical portion axially extending from the innerraceway surface, the inner ring is press-fit onto the wheel hub, theinner ring including another inner raceway surface formed on its outercircumference, the other inner raceway surface arranged opposite to theother double row outer raceway surface and the inner ring has aprojecting portion that projects to the inner side beyond the outermember; a double row rolling element is freely rollably containedbetween the raceway surfaces of the inner member and the outer member;the inner ring is secured to the wheel hub by a caulked portion, thecaulked portion is formed by plastically deforming an end of thecylindrical portion radially outward; the constant velocity universaljoint has an outer joint member having a cup-shaped mouth portion, ashoulder portion, forming the bottom of the mouth portion, and acylindrical shaft portion, axially extending from the shoulder portion,the shaft portion has an internal thread, the mouth portion, theshoulder portion, and the shaft portion are integrally formed in theouter joint member; face splines are formed at the respective end facesof the shoulder portion of the outer joint member and the caulkedportion, the face splines are supported with pressure by a fasteningbolt that abuts an outer side end face of the wheel hub and isthreadedly connected to the internal thread of the shaft portion, andthe double row rolling bearing and the constant velocity universal jointare coupled together in such a way that the double row rolling bearingand the constant velocity universal joint can transmit torque and areaxially separable; an inner seal and an outer seal sealing the inner andouter members at their respective ends; compressive remaining stress isplaced on the surfaces of the face splines as a result of surfacemodification; and an exterior seal mounted on the projecting portion ofthe inner ring at a position inside of the inner seal and beyond theouter member, the exterior seal covering the radial outside of the facesplines, the exterior seal in sliding contact with the shoulder portionof the outer joint member, the exterior seal sealing an engaging portionof the face splines, and the exterior seal is separate and spaced fromthe inner seal sealing the inner and outer members.
 2. The driving wheelbearing apparatus according to claim 1, wherein the exterior seal ismounted on the outside diameter of the inner ring or the inner ringmember, the exterior seal includes a metal core press-fit onto theoutside diameter of the inner ring or the inner ring member, a sealmember is made of synthetic rubber, the seal member is integrally bondedto the metal core by cure adhesion or the like, the seal member has anaxial lip, the axial lip makes elastic contact with the shoulder portionof the outer joint member, and thereby sealing the engaging portion ofthe face splines.
 3. The driving wheel bearing apparatus according toclaim 2, wherein the seal member has a side lip slidingly extendingradially outward, a stepped portion is formed in the shoulder portion ofthe outer joint member, and the side lip is brought into elastic contactwith the stepped portion.
 4. The driving wheel bearing apparatusaccording to claim 2, wherein the tip of the axial lip is formed intothe shape of a circular arc.
 5. The driving wheel bearing apparatusaccording to claim 2, wherein the seal member has a grease lip, and theengaging portion of the face splines is filled with grease.